High-frequency power amplifiers typically comprise several single high-frequency output-stage amplifiers which are connected to high-frequency output-stage components by couplers (power splitters and power couplers). Only in this manner is the required total power output achieved. The failure of one or more of these high-frequency output-stage amplifiers results in reduced output power, however, transmission—with reduced signal-to-noise ratio S/N at the reception site—is still possible with reduced output power. The remaining output power can be calculated with the formula Pout=Pnom*m2/n2, where Pout denotes the remaining output power, Pnom denotes the nominal output power when all output-stage amplifiers are functioning, [m] denotes the number of functional output-stage amplifiers and [n] denotes the total number of output-stage amplifiers.
By contrast, transmission is no longer possible in the event of a failure of a power-supply unit if this is not embodied in a redundant manner. Precisely such power-supply units are subject to a relatively high risk of failure, as they form the connection between the mains electricity supply and the component groups in the individual devices. The quality of the mains supply is highly variable, not only in different countries but also within industrial plants, so that large voltage fluctuations, voltage spikes or brief supply interruptions are not uncommon. Additionally, increasingly faster and more powerful component groups and, at the same time, the demand for more compact power-supply units have resulted in complex switching units which comprise many heavily loaded components and are accordingly subject to statistical failures. A redundant power supply for the power amplifier is therefore desirable in order to increase operational reliability.
A redundant arrangement of power-supply units which supply a number of independent high-frequency power amplifiers is known from U.S. Pat. No. 6,064,260. Every high-frequency power amplifier provides a power-supply unit, a high-frequency power stage and a linearizer, wherein the high-frequency power stage and the linearizer represent the load on the power-supply unit and are supplied with energy from the latter. At the same time, all power-supply units are connected to a power-supply bus. In the event of a failure of a power-supply unit, this generates an error signal which opens a switch and separates the power-supply unit from the load of the high-frequency power amplifier and the power-supply bus. The remaining power-supply units are dimensioned in such a manner that they can continue supplying the high-frequency power amplifier in which the power-supply unit failed with energy. In addition, a current sensor registers the current consumption of the connected load. If the current consumed is not within a defined range, this points to an error in the high-frequency power stage or the linearizer. A switch then separates the load from the power-supply unit of the power amplifier and from the power-supply bus.
The disadvantage of the arrangement according to U.S. Pat. No. 6,064,260 is that it is not possible to switch off individual output-stage amplifiers which together form a high-frequency power amplifier. The high-frequency amplifier must either continue to operate or must be switched off as a whole, wherein, in the latter case, it ceases to transmit a signal. No provision is made here for operation with reduced output power. In order to secure a redundancy, all power-supply units must be significantly oversized. If, for example, only two high-frequency power amplifiers are each connected to a power-supply unit via the power-supply bus, each power-supply unit must be designed for double the power in order to be able to supply the other power amplifiers with energy in the event of a failure. Otherwise one or both current sensors for the high-frequency amplifiers would report an error, which would lead to one or both high-frequency amplifiers being disconnected from the power-supply bus via the corresponding switch. But at least one high-frequency amplifier would completely cease to operate. In order to achieve a redundancy, the cost of the whole arrangement, in particular with power-supply units with an output of many kilowatts, increases significantly. If, for example, more than two high-frequency power amplifiers are connected to the power-supply bus, the output reserve of the power-supply units can be reduced to a certain extent, however, different power-supply units must be used in order to supply identical amplifier stages dependent on the number of individual power amplifiers. The different size of the power-supply units makes a unified housing design for a variable number of power amplifiers within one housing impossible. In the event of an error, the switches used still need to be able to switch off a short-circuit current of more than 100 A in some cases. The size and the costs for one such switch are therefore not negligible.